Use this one:
SELECT TABLE_NAME, PARTITIONING_TYPE, COLUMN_NAME, DATA_TYPE
JOIN USER_PART_KEY_COLUMNS ON NAME = TABLE_NAME
JOIN USER_TAB_COLS USING (TABLE_NAME, COLUMN_NAME)
where OBJECT_TYPE = 'TABLE';
The 5x performance hit for query 3 turned out as mistake. That was the puzzling bit and is resolved.
All the rest makes sense, though it's currently not going your way. The PRIMARY KEY is the culprit:
PRIMARY KEY (scedtime, node_id)
The manual suggests:
Create an index on the key column(s), as well as any other indexes you might want, on the partitioned ...